Extension Logo
Extension Logo
University of Minnesota Extension
https://extension.umn.edu

Raspberry leaf spot

Quick facts

  • Raspberry leaf spot is common and very damaging in certain raspberry varieties.
  • Leaf spots form on young leaves. Severely infected leaves fall off.
  • During humid summers, primocanes (first year canes) can lose up to 75% of their leaves causing the canes to stop growing.
  • These small canes produce less fruit and are likely to be damaged by winter injury.
  • To manage this disease, plant on a site with full sun and good air circulation. Plant in narrow rows, remove weeds, and thin plantings that have become overgrown.
  • In some varieties, the disease becomes worse each year unless it’s managed by cultural practices or fungicides.

How to identify leaf spot

  • Leaf spot
    Small dark green to black spots appear on the upper surface of young leaves.
  • As leaves age, leaf spots turn white to gray. The center of the spot may fall out, leaving small holes in the leaf.
  • Badly infected leaves curl downward at the edges and fall off.
  • Small brown spots sometimes form on canes close to the ground.

How does leaf spot survive and spread?

  • The fungus that causes leaf spot, Sphaerulina rubi, overwinters in infected leaf debris and in spots on canes.
  • Only young, growing leaves and canes can be infected.
  • Spores are spread by splashing water.
  • Leaf spot is common in years when it rains often.
  • The disease continues to spread all summer, as long as young leaves are present.
  • Leaf spot causes the most damage in summers with heavy rains in June and July.

How to manage leaf spot

First decide if the diseased leaves are on primocanes (first year canes) or floricanes (second year canes). Leaf spot is more serious if it’s on primocanes. The leaves on floricanes naturally die towards the end of harvest.

 | 

Michelle Grabowski, Extension educator and Thaddeus McCamant

Reviewed in 2019

Share this page:

© 2019 Regents of the University of Minnesota. All rights reserved. The University of Minnesota is an equal opportunity educator and employer.